a) Field of the Invention
This invention relates to iodoalkynyl carbamates which are useful as germicides for paints, leather, fibers and the like.
b) Description of the Related Art
U.S. Pat. No. 3,923,870 discloses iodoalkynyl carbamates of the general formula (1) EQU [IC.tbd.C--(CH.sub.2).sub.n OCONH].sub.m R (1)
where R is a substituted or unsubstituted alkyl, cycloalkyl, aryl or aralkyl group containing 1 to 20 carbon atoms and having a valence of m, and m and n are whole numbers of 1 to 3, and a process for the preparation of such compounds.
The process for the preparation of such compounds comprises the steps of iodinating an alkynol of the general formula (3) EQU kHC.tbd.C--(CH.sub.2).sub.n OH (3)
where n is as previously defined, with iodine to form an iodoalkynol of the general formula (4) EQU IC.tbd.C--(CH.sub.2).sub.n OH (4)
where n is as previously defined, and subsequently reacting the iodoalkynol with an isocyanate of the general formula (5) EQU R(NCO).sub.m ( 5)
where R and m are as previously defined.
As an alternative process, Japanese Patent Laid-Open No. 100354/'80 (European Patent No. 0014032) discloses a process comprising the steps of reacting an alkynol of the above general formula (3) with an isocyanate of the above general formula (5) to form an alkynyl carbamate of the general formula (2) EQU [HC.tbd.C--(CH.sub.2).sub.n --OCONH].sub.m R (2)
where R, m and n are as previously defined, and subsequently iodinating the alkynyl carbamate with an iodinating agent as described below to form a compound of the above general formula (1).
However, the former process has the disadvantage that many of the iodoalkynols formed as intermediate products produce heavy foam and are weakly explosive. Moreover, since iodination is effected by use of iodine, polyiodinated by-products are formed in addition to the iodoalkynol. These by-products cannot be removed in the succeeding step, so that they remain in the finally obtained iodoalkynyl carbamate and cause a reduction in purity.
On the other hand, the latter process is superior to the former one in that polyiodinated by-products are scarcely formed. However, since this process uses an iodinating agent comprising a mixture of sodium hypochlorite and an alkali metal iodide or a mixture of sodium hypochlorite, an alkali metal hydroxide and iodine, the following difficulties are encountered.
In this case, sodium hypochlorite acts as an oxidizing agent for the iodine ions which are formed during iodination or added as a starting material, and thereby produces iodine that is effective in the iodination of alkynyl carbamates. Where sodium hypochlorite is not used as a component of the above-described iodinating agent, a large excess (at least two moles per mole of the alkynyl carbamate) of iodine is required.
Moreover, at relatively high temperatures (e.g., 10.degree. C. or above), sodium hypochlorite acts as an oxidizing agent to convert iodine into hypoiodite ions and further iodate ions, and also acts as a chlorinating agent to form chlorine compounds as by-products.
As described above, the addition of sodium hypochlorite is indispensable for effective utilization of the iodine component. However, since sodium hypochlorite not only oxidizes iodine ions but may act as a chlorinating agent or an oxidizing agent, it is necessary to carry out the reaction at a temperature lower than 10.degree. C. Moreover, sodium hypochlorite involves a problem with stability, in that it tends to be converted into sodium chlorate during storage and thus reduced in purity. Accordingly, the utmost care must be taken in the storage of sodium hypochlorite.